INFLUENCE OF TRANSREACTION PROCESSES ON THE MORPHOLOGY OF SEMICRYSTALLINE ALIPHATIC AROMATIC POLYAMIDE BLENDS/

During the melt-extrusion of blends of aliphatic polyamide 46 (PA 46) and aromatic polyamide 61 (PA 61), transamidation reactions occur betw een the blend components. This yields polyamide copolymers consisting of crystallisable PA 46 and noncrystallisable PA 61 sequences. The eff ect of the copolymer formation on the semicrystalline morphology is st udied by time-resolved SAXS and WAXS measurements using synchrotron ra diation and by transmission electron microscopy. From WAXS patterns it is noticed that only an excess of PA 61 in the blends affects the PA 46 crystal unit cell at room temperature by hindering or inhibiting th e Brill-transition during cooling from the melt. Close to the melting or crystallisation point, the PA 46 crystal structure is independent o f the blend composition or thermal history. Consequently, the observed melting point depression cannot be ascribed to less perfect PA 46 cry stals, but to a smaller lamellar thickness of the crystallised PA 46 s equences which is confirmed by TEM. (C) 1998 Elsevier Science Ltd. All rights reserved.